(1) Field of the Invention
The present invention relates to a lighting device in which ambient light collected and captured in a light-collecting unit is converted into a transmitting light and guided to an object to be illuminated. The present invention also relates to a liquid crystal display device provided with the lighting device.
(2) Description of the Prior Art
Liquid crystal display panels are widely utilized for an information display unit in camcorders, digital cameras, and the like. For such liquid crystal display devices, generally, transmissive-type liquid crystal display panels have been employed. In a display panel for such appliances as camcorders and digital cameras, it is necessary to prevent a display defect caused by ambient light incident on the panels, since such appliances are often used under strong ambient light. Accordingly, it is essential that liquid crystal display panels used for such appliances have a high luminance. In view of this, Japanese Unexamined Patent Publication No. 10-123507 discloses an apparatus having the following configuration. In the apparatus, a light-collecting unit for collecting ambient light is provided on an upper face of the apparatus, and the ambient light collected in the light-collecting unit is guided to a back surface of a liquid crystal display panel using microprisms so as to illuminate the liquid crystal display panel from the back surface of the panel, for the purpose of increasing a brightness of the liquid crystal display panel.
However, in the above-described device of prior art, the light-collecting unit is placed at the back of the liquid crystal display panel and formed in a rectangular-like shape on the upper face of the apparatus, and ambient light is directly guided to the back surface of the liquid crystal display panel. Therefore, the light-collecting unit cannot be made large, restricted to a relatively small area of a rectangular-like shape. It is noted here that the size of an area of the light-collecting unit directly influences a brightness of the display panel. Accordingly, the prior art device has at least a drawback that the improvement in brightness is insufficient since the light-collecting unit cannot be made large.
In view of the foregoing and other drawbacks in prior art, it is an object of the present invention to provide a lighting device and a liquid crystal display device in which, unlike conventional light-collecting units, two separate units each having a different function (i.e., a light-collecting unit for collecting and capturing ambient light, and a light-guiding unit, connected to the light-collecting unit, for guiding the light to a liquid crystal display panel) are provided to increase an occupied area of the light-collecting unit and thereby to achieve an increased brightness.
These and other objects are accomplished by providing a lighting device capable of utilizing ambient light for illuminating an object to be illuminated, comprising:
a light-collecting unit for collecting ambient light, and
means for converting at least a part of the ambient light into a transmitting light transmitted in the light-collecting unit, the means for converting being provided in the light-collecting unit.
By employing such a configuration, ambient light is captured and converted into a transmitting light in the light-collecting unit, and thereby ambient light is efficiently guided to the object to be illuminated.
The above-described lighting device according to the invention may further comprise a plurality of means for redirecting a proceeding direction of light, provided in a light path between the light-collecting unit and the object to be illuminated, and may be such a device in which a proceeding direction of the ambient light emitted from the light-collecting unit is redirected a plurality of times by the means for redirecting, so that the ambient light is guided to the object to be illuminated.
In the above-described configuration, the ambient light from the light-collecting unit is guided to the object to be illuminated by the means for redirecting, and thereby many variations in relative positions of the light-collecting unit and the object to be illuminated are made possible. The means for redirecting is not limited to a means that redirects a light by reflection, but other variations, for example, such means that redirects a light by refraction, diffraction, and the like may be employed.
The above-described lighting device may be such a device in which the light-collecting unit comprises a flat outward surface on which the ambient light is incident and a serrated reflecting surface provided on a surface opposite to the outward surface.
By employing the above configuration, ambient light can be efficiently converted into a transmitting light.
The above-described lighting device may be such a device in which the means for redirecting a proceeding direction of light is a reflecting surface for reflecting the ambient light.
The present invention also provides a liquid crystal display device capable of utilizing ambient light for illuminating a liquid crystal panel provided in a casing, comprising:
a light-collecting unit for collecting the ambient light and converting at least part of the ambient light into a transmitting light transmitted in the light-collecting unit, and
a light-guiding unit for guiding the transmitting light to the liquid crystal panel by redirecting a light path of the transmitting light.
By employing the above configuration, unlike conventional light-collecting units, two separate units each having a different function (i.e., a light-collecting unit for collecting and capturing ambient light, and a light-guiding unit, connected to the light-collecting unit, for guiding the light to a liquid crystal display panel) are provided in the device. Accordingly, an occupied area of the light-collecting unit is increased, and thereby an increased brightness is achieved.
A liquid crystal display device according to the invention may be such a device in which the light-collecting unit comprises a serrated reflecting surface provided on a surface of the light-collecting unit opposite to an outward surface of the light-collecting unit on which the ambient light is incident.
The serrated reflecting surface converts ambient light into a transmitting light to transmit the light to the light-guiding unit.
A liquid crystal display device according to the invention may be such a device in which the light-collecting unit is provided on an upper face of the casing of the liquid crystal display device.
By employing such a configuration, ambient light coming from an upward direction can be efficiently guided to the liquid crystal display panel.
A liquid crystal display device according to the invention may be such a device in which the light-collecting unit is provided on an upper face of the casing of the liquid crystal display device.
By employing such a configuration, ambient light coming from an upward direction and a sideward direction can be efficiently guided to the liquid crystal display panel.
A liquid crystal display device according to the invention may be such a device in which:
the light-collecting unit comprises a first light-collecting unit formed on a face of the casing opposite to a face on which the liquid crystal panel is provided, and a second light-collecting unit formed on an upper face of the casing, and
one of the end faces of the second light-collecting unit is connected to one of the end faces of the first light-collecting unit, and the other end face of the second light-collecting unit is connected to one of the end faces of the light-guiding unit.
By providing the first light-collecting unit and the second light-collecting unit as described above, more ambient light can be collected, and a brightness of the liquid crystal panel is further increased.
A liquid crystal display device according to the invention may further comprise:
a flat reflecting surface formed at a connecting part of the first light-collecting unit and second light-collecting unit and placed in an inclined position so that a light from the first light-collecting unit is reflected and guided to the second light-collecting unit.
By employing such a configuration, a transmitting light captured in the first light-collecting unit can be efficiently transmitted to the light-guiding unit through the second light-collecting unit.
A liquid crystal display device according to the invention may be such a device in which:
the second light-collecting unit has a flat transparent outward surface and a flat reflecting surface opposed to the outward surface, the flat reflecting surface downwardly inclined towards the light-guiding unit,
the first light-collecting unit has a flat transparent outward surface on which ambient light is incident and a first serrated reflecting surface comprising a plurality of first inclined surfaces and a second serrated reflecting surface comprising a plurality of second inclined surfaces, the first and second serrated surfaces both being formed on a surface opposite to the outward surface and the first serrated reflecting surface being disposed upward of the second serrated reflecting surface on the casing, the plurality of first inclined surfaces and the plurality of second inclined surfaces inclined in directions opposite to each other, and
the plurality of first inclined surfaces and the flat reflecting surface in the second light-collecting unit are commonly inclined towards the light-guiding unit.
By employing such a configuration, ambient light incoming from a direction forward and obliquely upward can be efficiently captured and converted into a transmitting light by the second inclined surfaces, and the transmitting light can be transmitted to the second light-collecting unit.
A liquid crystal display device according to the invention may be such a device in which:
the serrated reflecting surface in the first light-collecting unit has a first serrated surface comprising a plurality of first inclined surfaces and second serrated reflecting surface comprising a plurality of second inclined surfaces, the plurality of first inclined surfaces and the plurality of second inclined surfaces inclined in directions opposite to each other, the first serrated reflecting surface being disposed upward of the second serrated reflecting surface on the casing,
the serrated reflecting surface in the second light-collecting unit comprises a plurality of inclined surfaces, and
the plurality of first inclined surfaces in the first light-collecting unit and the plurality of inclined surfaces in the second light-collecting unit are commonly inclined towards the light-guiding unit.
In the above-described configuration as well, ambient light incoming from a direction forward and obliquely upward can be efficiently captured and converted into a transmitting light by the second inclined surfaces, and the transmitting light can be transmitted to the second light-collecting unit.
A liquid crystal display device according to the invention may be such a device in which:
the second light-collecting unit has a flat transparent outward surface and a flat reflecting surface opposed to the outward surface, the flat reflecting surface downwardly inclined towards the light-guiding unit, and
the first light-collecting unit has a flat transparent outward surface and a flat reflecting surface opposed to the outward surface, the flat reflecting surface inclined in such a manner that a thickness of the first light-collecting unit is gradually reduced towards a top of the casing.
In the above-described configuration, ambient light incoming from a direction forward and obliquely upward can be efficiently captured and converted into a transmitting light.
A liquid crystal display device according to the invention may be such a device in which:
the second light-collecting unit has a flat transparent outward surface and the serrated reflecting surface, and
the first light-collecting unit has a flat transparent outward surface and a flat reflecting surface opposed to the outward surface, the flat reflecting surface inclined in such a manner that a thickness of the first light-collecting unit is gradually reduced towards a top of the casing.
In the above-described configuration as well, ambient light incoming from a direction forward and obliquely upward can be efficiently captured and converted into a transmitting light.
A liquid crystal display device according to the invention may be such a device in which the serrated reflecting surface comprises a plurality of inclined surfaces in which an inclined angle thereof is varied.
In such a configuration, by making small the inclined angle of the inclined surfaces, more transmitting light can be produced and efficiently transmitted to the light-guiding unit.
A liquid crystal display device according to the invention may be such a device in which the inclined angle is in the range of 5xc2x0 to 50xc2x0.
The inclined angle is restricted since if the angle is out of the foregoing range, the efficiency of converting ambient light into a transmitting light is considerably deteriorated.
A liquid crystal display device according to the invention may be such a device in which the serrated reflecting surface has a shape such that when viewed from the top, a plurality of stripe-like lines are formed.
Further, each of the plurality of stripe-like lines may form a V-like shape whose inferior angle is faced to the light-guiding unit.
By employing such a configuration, ambient light can be focused in a direction of the center of the light-collecting unit. Therefore, a light escaping outside from an end face of the light-collecting unit is reduced and the efficiency of capturing light is increased, and consequently the efficiency of light utilization is improved.
A liquid crystal display device according to the invention may be such a device in which the light-guiding unit guides the transmitting light from the light-collecting unit to a back of the liquid crystal panel so as to illuminate the liquid crystal from the back of the liquid crystal panel.
By employing this configuration, the liquid crystal display device can employ a transmissive-type liquid crystal panel.
In the above-described liquid crystal display device, the light-guiding unit may have a flat reflecting surface formed on an outward surface thereof and a prism array formed on a surface opposite to the outward surface, and the light-guiding unit may direct the transmitting light from the light-collecting unit towards the back of the liquid crystal panel.
In the above-described configuration, ambient light is guided from the prism array towards the back of the liquid crystal panel, and thereby the light can be efficiently guided to the back of the liquid crystal display panel.
The above-described liquid crystal display device may further comprise a flat inclined reflecting surface formed in an area from the outward surface to an end face thereof adjacent to the liquid crystal panel.
As in the above-described configuration, when the light-guiding unit has a flat inclined reflecting surface in an area from the outward surface to an end face thereof adjacent to the liquid crystal panel, a light path of the transmitting light can be changed thereby, and the transmitting light can be efficiently guided to the back of the liquid crystal panel.
A liquid crystal display device according to the invention may be such a device in which:
the light-guiding unit comprises a light guiding plate disposed in front of the liquid crystal panel so that the transmitting light from the light-collecting unit is guided to the light guiding plate and emitted to the liquid crystal panel to illuminate the liquid crystal panel.
By employing this configuration, the liquid crystal display device can employ a reflective-type liquid crystal panel.
A liquid crystal display device according to the invention may be such a device in which at least a portion of the light-collecting unit is movable.
By employing such a configuration, the light-collecting unit can be set at a most suitable position so that ambient light is more efficiently collected.
A liquid crystal display device according to the invention may be such a device in which at least a surface of the light-collecting unit is composed of a semi-transparent material.
Further, a liquid crystal display device according to the invention may be such a device in which at least a portion of a surface of the light-collecting unit is composed of a colored semi-transparent material.
Even when a surface of the light-collecting unit is composed of a semi-transparent or colored semi-transparent material, the advantageous effect of collecting ambient light can be sufficiently attained.